Touch panels have become ubiquitous in portable computing and industrial applications. Capacitive touch systems have been developed to detect inputs with little or no activation force. A typical implementation of a conventional capacitance type touch panel is illustrated in FIG. 1. The touch panel 100 includes a drive electrode 102 and a sense electrode 104, across which a capacitance 106 occurs between the two electrodes. The drive electrode 102 and the sense electrode 104 may be formed on a transparent substrate such as the viewing surface of a display screen or a non-transparent surface such as an interactive whiteboard. An electrical signal may be sent to the drive electrode 102 and a response signal may be detected on the sense electrode 104. Touch panel 100 may be coupled to circuitry configured to provide the electrical signal and measure the response signal. The circuitry may be configured to determine the capacitance 106 between the two electrodes based on the response signal. A finger 108 or other input instrument (e.g. a stylus) in proximity to the electrodes may cause a large drop in the capacitance 106 and change the response signal that can be detected by the circuitry. For example, if an input object such as the finger 108 is connected to ground, as is the case for example of a human finger connected to a human body, the effect is a reduction of the amount of capacitive coupling in between the drive electrode 102 and the sense electrode 104, and hence a reduction in the magnitude of the signal measured by the circuitry attached to the sense electrode 104.
FIG. 2 is a schematic drawing depicting a touch panel configured to detect non-conductive objects. A non-conductive object causes sense electrodes positioned at near coupling distances relative to drive electrodes to have reduced capacitance, and sense electrodes with increased coupling distances to have increased capacitance. The effect depends on the precise geometry of the electrodes. If the sense electrodes are joined, these effects tend to cancel out. To detect non-conductive objects, the touch panel includes the drive electrode 102, a first sense electrode 110, and a second sense electrode 112. A voltage stimulus may be applied to the drive electrode 102, and the voltage stimulus causes a potential difference between the first sense electrode 110 and the second sense electrode 112. A first mutual capacitance, CA, forms over a first coupling distance, w1, and a second mutual capacitance, CB, forms over a second coupling distance, w2. A non-conductive input object, such as a gloved finger 109, may be detected using a first change in capacitance, ΔCA associated with the first sense electrode 110, and a second change in capacitance ΔCB associated with the second sense electrode 112. For a non-conductive object, the first change in capacitance may be negative and the second change in capacitance may be positive. Circuitry coupled to the electrodes may determine an impedance to ground, which tends to be about 1 GOhm or less at the operating frequency of the touch panel as associated with a conductive object, and an impedance to ground greater than about 1 GOhm as associated with a non-conductive object.
FIG. 3 shows a plan view of an electrode arrangement 301 of a conventional capacitive touch panel. For illustrative purposes, a 2×2 electrode array is shown, although any suitable number of rows “M” and columns “N” may be employed as is suitable for any particular application.
The conventional capacitive touch panel 301 includes a first sense electrode column 300, a second sense electrode column 302, a first drive electrode row 304 and a second drive electrode row 306. To detect non-conductive objects, the sense electrode columns include a first and second dual-function sense electrode and the drive electrode rows are formed by a first and second dual-function drive electrode. The first sense electrode column 300 includes a first dual function sense electrode A1 coupled to the circuitry using signal wire 310, and a second dual function sense electrode B1 coupled to the circuitry using signal wire 320. The first sense electrode A1 is adjacent to a first drive electrode D1 that is coupled to the circuitry using signal wire 330. The second sense electrode B1 is adjacent to a second drive electrode D2 that is coupled to the circuitry using signal wire 335. Each sense electrode is in a “bow-tie” configuration coupled, for example, by a conductive line 332 that extends between the two halves of the bow-tie shape. Each drive electrode similarly is in an “hourglass” configuration and coupled, for example, by a second conductive line 334 that extends between the two halves of the hourglass shape.
Comparably, the second sense electrode column 302 includes a first dual function sense electrode A2 coupled to the circuitry using signal wire 315 and a second dual function sense electrode B2 coupled to the circuitry using signal wire 325. The first sense electrode A2 is adjacent to a third drive electrode D3 that is coupled to the circuitry using signal wire 340, and the second sense electrode B2 is adjacent to a fourth drive electrode D4 that is coupled to the circuitry using signal wire 345. Here, there are two drive electrode signal wires for each row of drive electrodes, M, and two signal wires for each column of sense electrodes, N. The arrangement is symmetric in the sense that all elements in the same row have the same sense electrode (bow tie elements), and all elements in the same column have the same drive electrode (hourglass elements). Each row and column further are connected with two signal lines. With such configuration, the total number of signal wires may be determined using the total number of rows, M, and columns, N:Total Signal Wires=2M+2N. 
To illustrate, the number of rows, M, and columns, N, in a capacitive touch panel for a laptop screen may be approximately 50-70. For instance, a laptop with 60 drive electrode rows, (M=60) and 60 sense electrode rows (N=60) will have 240 signal wires. Each signal wire will require connectors, driving and sensing circuitry, and processor time to complete the signal processing. This required large number of signal wires has limited the advantages of conventional configurations. Existing technologies utilize complex signal wire arrangements to drive and sense non-conductive inputs to capacitive touch panels. The complexity results in increased power usage, and increased engineering, manufacturing, repair, and replacement costs. Accordingly, improved systems and methods are needed in the art.